1. Field of the Invention
The present invention relates to pivotal hand tools, such as pliers, cutters and the like and, in particular, to pivot joints for such tools.
2. Description of the Prior Art
There are many types of pivotal hand tools, such as various types of pliers and cutters, and they all typically include a pair of lever members each having a handle portion at one end and a jaw portion at the other end and arranged in intersecting relationship for pivotal movement about a pivot axis through a point of interconnection so that the jaw portions cooperate with each other. Various types of pivot joints are provided for such hand tools. A common type of joint includes arranging the lever members in overlapping relationship with aligned openings therethrough and a pivot post extending through the aligned openings. The post may be in the form of a rivet, interlocking threaded fasteners and the like. In such pivot joints, the lever members are moveable relative to one or more parts of the pivot joint, causing frictional wear which results in loosening of the joint and difficulty in maintaining control and tolerances. In order to minimize such wear, it is frequently necessary to lubricate such prior pivot joints.
Furthermore, in pivotal hand tools such as cutters and the like, it is necessary that the jaws and handles be normally biased to an open condition, which necessitates the use of separate bias means. This adds to the complexity and expense of manufacture and assembly of the tool.
It is known to use flexural pivot assemblies in certain types of pivotal devices. Such pivot assemblies include a pair of cylindrical members and two thin flexural leaf spring elements disposed in crossed but non-contacting relationship in the cylindrical members, with each spring element having edge portions respectively fixed to the cylindrical members. The spring elements have very low column strength and are easily subject to damage during mounting of the flexural pivot assembly in associated bodies which are to be pivotally movable with respect to each other.